According to the Association of American Feed Control Officials (AAFCO) “meal” is defined to be “a dry-rendered product” from the exact same definition as “whole meat”. Essentially, it is the same product, only in a dried form. Whole meat contains about 70% water, leaving the meat to contain about 18% protein, and 5% fat. By removing the moisture, meal may have between about 1% and 10% and up to 20% water, in the neighborhood of 50% protein and above, and about 10%-15% fat.
Rendering is a process that converts waste animal tissue into stable, value-added materials. Rendering can be carried out on an industrial, farm, or kitchen scale. The general process is centuries old and has been carried out for many centuries, primarily for soap and candle making. The earliest rendering was done in a kettle over an open fire. This type of rendering is still done on farms to make lard (e.g. pork fat) for food purposes.
With the development of steam boilers, it was possible to jacket the kettle to make a higher grade product and to reduce the danger of fire. A further development came in the nineteenth century with the use of the steam “digester” which was simply a tank used as a pressure cooker in which live steam was injected into the material being rendered. This process is a wet rendering process called “tanking” and was used for both edible and inedible products, although the better grades of edible products were made using the open kettle process. After the material is “tanked”, the free fat is run off, the remaining water (“tank water”) run into a separate vat, and the solids removed and dried by both pressing and steam-drying in a jacketed vessel.
Next, continuous dry processes were introduced. Then, in the 1980s, high energy costs popularized the various “wet” continuous processes. These processes were more energy efficient and allowed the re-use of process vapours to pre-heat or dry the materials during the process.
The majority of tissue processed in rendering plants comes from slaughterhouses. The rendered material can include the fatty tissue, bones, and offal, as well as entire carcasses of animals. The most common animal sources are beef, pork, sheep, and poultry. The rendering process simultaneously dries the material and separates the fat from the bone and protein. A rendering process typically results in a fat which may include yellow grease, choice white grease, or bleachable fancy tallow, etc. and a protein meal which may be any of meat and bone meal, poultry byproduct meal, etc. Animal by-product meal consists of rendered animal tissues that don't contain hair, horns, hoofs, hide trimmings, manure, or intestinal contents or extraneous materials. Poultry (or chicken or turkey) by-product meal: consists of ground, rendered, clean parts of the carcass of slaughtered poultry such as necks, feet, undeveloped eggs and intestines. It cannot contain feathers. Rendering plants often also handle other materials, such as slaughterhouse blood, feathers and hair, but do so using processes distinct from true rendering.
When the rendering product will be incorporated in food products or pet foods, the rendering is most often carried out in a continuous process or batch process. This helps to maintain the integrity of the proteins and amino acid profiles. The edible fat materials (generally fat trimmings from meat cuts) are heated, and then the fat is separated often using two or more stages of centrifugal separation. The solids separated from the fat may be used in food products, pet foods, and others products depending on the original materials. The separated fat may be used in food products, or if in surplus, it may be diverted to soap making operations.
An alternative process cooks slaughterhouse offal to produce a thick, lumpy “stew” which is then sold to the pet food industry to be used principally as tinned cat and dog foods. Such plants are notable for the offensive odor that they can produce and are often located well away from human habitation.
U.S. Pat. No. 7,329,425 discloses a process for on-site digestion of spent hens employing an enzymatic digest within a given range of pH, temperature and enzymes. U.S. Pat. No. 7,226,425 discloses apparatus designed to process spent hens, which apparatus optionally includes means to store, alter the pH of, and mix an enzyme digest; grind spent chickens and combine with the enzyme digest; circulate ground spent hens along with the digest through a chopper pump and allow digestion to progress, and thereafter dry the product. The enzyme digest comprises blood, enzyme, inedible egg. Another means of achieving the digested products includes a digest comprising blood, enzymes, and offal. Feathers, heads, backs, necks and wings may be included in the digest process and the result may or may not be dried. The result of this digest is rich in protein and amino acids.
Poultry by-product meal, as mentioned herein, has long been known to contain an amino acid profile energy content, total lysine content and ash content which is suitable for animal feed but could be improved dramatically if the total energy content could be increased, or the amino acid profile tailored to the end use, or the ash content reduced. Poultry byproduct meal includes a variety of advantages when used as an animal feed or feed additive but is certainly not the only possible source.
The present invention differs from the above referenced inventions and others similar in that these prior compositions do not allow for or provide a method for controlling or tailoring amino acid profiles, ash content or total energy content in animal feeds such as pet foods. To date, pet foods that include rendered products as additives have a relatively high ash inclusion. It would be desirable for the additive or ingredient to include a higher level of usable (digestible) protein (e.g. lower molecular weight) and a higher available energy content and a lower ash content than poultry byproduct meal, other rendered products, or chicken meal.
What was needed was a feed additive having an adjustable amino acid profile which is also palateable to the animals to which it is fed, which is easily stored, and predictable in animal food value, and which can be used to customize certain food values of an animal feed.
The objectives of the present invention are, together or separately, to provide a feed additive or flavor product which allows animal feed to comprise predictable and tailored usable energy content; altered and beneficial amino acid profiles, lower ash content; higher total lysine; and lower molecular weight than typically expected for feed resulting from a rendering process.